1. Field of the Invention (Technical Field)
The present invention relates to methods and apparatuses to control antenna polarization states.
2. Description of Related Art
Multiple polarization antennas are typically implemented by either mechanical switches, electronic phase shifters, or by having a dedicated feed port for each polarization. Polarization diversity can also be achieved by means of software processing to combine the orthogonal antenna polarization data sample outputs as a post processing event. Mechanical switches degrade over time and have limited high frequency applications, while electronic phase shifters are relatively expensive and many are able only to adjust phase in discrete increments resulting in some degree of polarization degradation. Defining dedicated antenna feed points for each polarization results in the disadvantage of being inefficient since the power available is divided amongst the various polarization assignments. And, because a software solution requires a post processing schedule, the results are not real time while requiring a relatively complex investment in interface technology. The present invention places all of the available power into the desired polarization and eliminates the limitations associated with mechanical switches and discrete electronic phase shifters. Furthermore, by controlling the phase in a fine analog sense, a more pure polarization sense is obtained.